Persons who work in polluted environments commonly wear respirators to protect themselves from inhaling airborne contaminants. Respirators typically have a fibrous or sorbent filter that is capable of removing particulate and/or gaseous contaminants from the air. When wearing a respirator in a contaminated environment, wearers are comforted with the knowledge that their health is being protected, but they are, however, contemporaneously discomforted by the warm, moist, exhaled air that accumulates around their face. The greater this facial discomfort is, the greater chances are that the wearer may remove the respirator from their face to alleviate the unpleasant condition. To reduce the likelihood of this occurrence, respirator manufacturers often install an exhalation valve on the mask body to allow the warm, moist, exhaled air to be rapidly purged from the mask interior. The rapid removal of the exhaled air makes the mask interior cooler, which, in turn, benefits worker safety.
For many years, commercial respiratory masks have used “button-style” exhalation valves to purge exhaled air from mask interiors. The button-style valves typically have employed a thin, circular, flexible flap as the dynamic mechanical element that lets exhaled air escape from the interior gas space. The circular flap has been centrally-mounted to a valve seat through a central post. Examples of button-style valves are shown in U.S. Pat. Nos. 2,072,516, 2,230,770, 2,895,472, and 4,630,604. When a person exhales, a circumferential portion of the flap is lifted from the valve seat so that the air can rapidly pass from the interior gas space into the exterior gas space.
Button-style valves have represented an advance in the attempt to improve wearer comfort, but investigators have made other improvements, an example of which is the “butterfly-style” valve shown in U.S. Pat. No. 4,934,362 to Braun. The valve described in the Braun patent uses a parabolic valve seat and an elongated flexible flap mounted in butterfly fashion.
After the Braun development, another innovation was made in the exhalation valve art by Japuntich et al.—see U.S. Pat. Nos. 5,325,892 and 5,509,436. The Japuntich et al. valve used a single flexible flap that is mounted off-center in cantilevered fashion to minimize the exhalation pressure that is required to open the valve. When the valve-opening pressure is minimized, less power is required to operate the valve, which means that the wearer does not need to work as hard to expel exhaled air from the mask interior when breathing—see also, U.S. Pat. No. 7,493,900 to Japuntich et al.
Other valves that have been introduced after the Japuntich et al. valve also have used cantilevered mounted flaps—see U.S. Pat. Nos. 5,687,767 and 6,047,698. In yet another development, the seal surface of the valve seat has been made from a resilient material that allows a thinner, yet stiffer flap to be used, which improves the valve efficiency—see U.S. Pat. No. 7,188,622 to Martin et al.
Although the evolution of exhalation valve design has centered mainly around structural changes relative to the valve seat and the mounting of the flap to it, investigators also have made structural changes to the flap itself to enhance valve performance. In U.S. Pat. Nos. 7,028,689 and 7,013,895 to Martin et al., multiple layers were introduced into the flap to create a thinner, more dynamic flap, which allowed the valve to open easier under less pressure. Ribs and a pre-curved, non-uniform, configuration also have been provided in the flap construction to provide good performance—see U.S. Pat. No. 7,302,951 to Mittelstadt et al. In U.S Patent Publication No. 2009/0133700 to Martin et al., slots have been provided in the valve flap at the hinge to improve valve performance. Also, in U.S. Published Application 2012/0167890A to Insley et al., the flap was ablated in selected areas to achieve desired valve performance. Flaps also have been made of an optical film, which causes the flap to flash so that users can readily detect proper valve operation—see U.S. Patent Application 61/846,456 to Martin et al.
Respirator designs come in a variety of shapes and configurations and the design is often influenced by the orientation and placement of the filter cartridges and any exhalation valve that is placed on the mask body. Cantilevered valves, for example, are commonly oriented vertically on the mask body, with the free end of the flap pointed downward. If oriented otherwise, the exhaled air may have the opportunity to fog a user's eyewear. Valve designs for high performance exhalation valves therefore can place constraints on mask body design. A new valve that can deliver exceptional valve performance, like a cantilevered valve, without having to be oriented vertically can help to alleviate constraints in valve design. The present invention described below has been created to provide such a valve.